Sigfredo “Siggy” Gonzalez — a convict-turned-confidential witness against Assemblyman Eric Stevenson — learned his criminal craft at the knee of former state Sen. Pedro Espada.

Gonzalez, 44, was employed in 2009-2010 as community-outreach manager for Espada, who was convicted last year on federal charges of looting Medicaid funds from a Bronx health- care network he ran.

Gonzalez also worked for Bronx Sen. Ruben Diaz Jr. when Diaz served in the Assembly in 1997-98, state records show. A top aide to Diaz was sentenced yesterday to plundering taxpayer funds from two social-service groups founded by the senator.

Gonzalez also has ties to former Bronx Democratic chairman and Assemblyman José Rivera, who backed him as a district leader, sources said.

Gonzalez was trounced in 2008 when he ran a primary against then-incumbent Bronx Assemblyman Michael Benjamin, who stepped down in 2010. Stevenson now occupies that South Bronx seat.